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# Hard S1 exam question Watch

1. QP:
MS:

Question 7c is a killer and is so so hard! I understand 7a and 7b, but just not c. I have no idea on how to do it . Please can someone explain how you do it.

THANKS
2. (Original post by krisshP)
Question 7c is a killer and is so so hard! I understand 7a and 7b, but just not c. I have no idea on how to do it . Please can someone explain how you do it.

THANKS
Think of the graph as three areas, call them A,B,C, divided by the two vertical lines.

You know what the total area under a pdf is.

You know what B is.

and you're told a relationship between A and C.

See what you can do.
3. (Original post by krisshP)
QP:
MS:

Question 7c is a killer and is so so hard! I understand 7a and 7b, but just not c. I have no idea on how to do it . Please can someone explain how you do it.

THANKS

If you know the area between 79-a and 79+b is 0.6463, then the rest of the area is 1-0.6463.

You also know the ratio of the area behind 79-a to the area past 79+b is in a ratio of 1:2 - so use simple ratios to find out the area behind 79-a.
4. (Original post by ghostwalker)
Think of the graph as three areas, call them A,B,C, divided by the two vertical lines.

You know what the total area under a pdf is.

You know what B is.

and you're told a relationship between A and C.

See what you can do.
I'll do this soon and see what happens. Btw what do you mean by pdf? Are you just talking about the are under the normal distribution curve?
Thanks!
5. (Original post by ghostwalker)
Think of the graph as three areas, call them A,B,C, divided by the two vertical lines.

You know what the total area under a pdf is.

You know what B is.

and you're told a relationship between A and C.

See what you can do.
It worked like a charm
Thanks so much!
6. (Original post by krisshP)
Btw what do you mean by pdf? Are you just talking about the are under the normal distribution curve?
Thanks!
The normal curve is a pdf, a probability density function. And the total area under any pdf is 1.

(Original post by krisshP)
It worked like a charm
Thanks so much!
You're welcome.

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